Bistable crosspoint matrix

ABSTRACT

A cover sheet is placed over the crosspoint relays within a crosspoint matrix. The cover sheet has a particular design which completely covers the crosspoints near the center of the matrix and only partially covers the crosspoints near the edges of the matrix. The crosspoints at the corners are not covered at all. The differences in the pickup and dropout values between the center, edge, and corner crosspoints is thereby eliminated.

\ United States Patent 1 Hoffmann et al.

[ BISTABLE CROSSPOINT MATRIX [75] Inventors: Walter Hoffmann, Munklingen;

Hans-Dieter Pfeil, Mainz; Wolfgang Mecklenberg, Asperg, all of Germany [73] Assignee: International Standard Electric Corporation, New York, NY.

22 Filed: Nov. 23, 1973 211 Appl. No.: 418,643

[30] Foreign Application Priority Data Dec. 7, 1972 Germany 2260002 [52] US. Cl. 335/236, 335/112 [51] Int. Cl. H0lh 3/12 [58] Field of Search 335/112, 152, 2.36;

340/166 C, 174 S; 317/101 CE [56] References Cited UNITED STATES PATENTS 3,061,696 10/1962 Peek Jr. ..335/236 Mar. 4, 1975 3 3,439,301 4/1969 Kudo et al. 335/112 3,445,728 5/1969 .lorgensen 335/152 Primary E.\'aminer-Harold Broome Attorney, Agent, or Firm-John T. OHalloran; Menotti J. Lombardi, Jr.; R. A. Menelly v [57] ABSTRACT A cover sheet is placed over the cr osspoint relays within a crosspoint matrix. The cover sheet has a particular design which completely covers the crosspoints near the center of the matrix and only partially covers the crosspoints near the edges of the matrix. The crosspoints at the corners are not covered at all. The differences in the pickup and dropout values between the center, edge, and corner crosspoints is thereby eliminated.

4 Claims, 4 Drawing Figures W'ENIEDHAR 41915 3, 869 687 SHEET 1 BF 2 PATENTEDIAR 1915 SHEET 2 [If 2 7 l BISTABLE CROSSPOINT MATRIX BACKGROUND OF THE INVENTION The present invention relates to a matrix with bistable crosspoint devices arranged in rows and columns, each of which is associatedwith a coil and a permanent magnet. An electric contact particularly designed for use in such crosspoint devices is described in a copending application by W. Mecklenburg et al. Ser. No. 417,984 filed Nov. 21, 1973, entitled Magnetically Actuated Sealed Contact, assigned to the assignee of the present invention.

A crosspoint relay, for the purpose of this invention, comprises an electromagnetically actuated contact wired in a'crosspoint switching configuration or matrix. A crosspoint matrix therefore consists of an ordered array of a plurality of contacts having an equal number of rows and columns and wired in a crosspoint switching configuration. The term crosspoint hereinafter refers to a crosspoint relay, and the term crosspoint matrix refers to a matrix array of crosspoint relays.

The uneven distribution of magnetic fields due to the additive coupling of the magnets corresponding to adjacent permanent magnets within the center of the matrix, and the absence of this magnetic coupling at the edges and corners of the matrix causes a mutual uneven distribution of the amount of magnetic force required to close the contacts (pickup values) and to open the contacts (dropout values) within the matrix.

In cases where bistable crosspoints are arranged closely adjacent in a matrix, the stray magnetic fields of the permanent magnets will influence the pickup and dropout values of the individual crosspoints to different extents. The static pickup and dropout values of the individual crosspoint contactsare displaced due to the influence of stray magnetic fields. At the edges and the corners of the matrix the displacement of these static values of the crosspoints is less than that of the crosspoints arranged in the center of the matrix and which are on all sides surrounded by neighbors. This uneven distribution in the pickup and dropout values can be detrimental in the crosspoint matrix since the electric current used to energize the electromagnetic relays is the same for all the relays within the matrix. The resulting pickup and dropout applied magnetic forces corresponding to the electromagnets within the matrix are equivalent for each crosspoint. It can be seen therefore that the crosspoints at the edges and corners of the relay may fail to pick up when the crosspoints close to the center of the matrix pickup in response to a particular electric pickup current and the crosspoints near the center may fail to drop out when the same electric dropout current is applied. By way of a suitable adjustment, i.e. by a weakening of the respective permanent magnets, the variation of the static values could be taken into consideration at the individual crosspoints prior to equipping the matrix. This measure, however, would require a process of sorting out the permanent magnets according to their center, edge and corner positions, causing the adjustment and testing to be rendered more expensive.

OBJECT OF THE INVENTION It is an object of the present invention to provide a matrix in which the aforementioned differences in the static values of the individual crosspoints are reduced in an inexpensive and effective manner.

SUMMARY OF THE INVENTION According to the invention this is accomplished by arranging a common cover sheet to completely cover the permanent magnets of the crosspoints arranged in the center of the matrix, and to partly cover the permanent magnets of the crosspoints arranged at the edges and corners of the matrix. The cover sheet is made from a material which is capable of shunting the magnetic fields of the neighboring permanent magnets and is arranged to lay parallel with the plane of the magnetization axes of the permanent magnets.

According to one embodiment of the invention the cover sheet covers half of the permanent magnets of the crosspoints arranged at the edges of the matrix, while the permanent magnets of the crosspoints arranged at the corners of the matrix are not covered by the cover sheet at all so that the magnetic field of the permanent magnets are shunted to a greater extent near the center of the matrix than at the edges and corners thereof. 7

In further embodying the invention the permanent magnets as associated with the crosspoints in the rows are polarized in the same sense, while those in the columns are polarized in the opposite sense.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagramatic view ofa matrix with 8 times 8 crosspoint relays showing the position of the cover sheet relative to the matrix;

FIG. 2 is a graphic representation of the pickup and dropout values of the crosspoint relays of a matrix without a cover sheet as compared to the value of an individual crosspoint relay;

FIG. 3 is a graphic representation of the pickup and dropout values of the crosspoint relays of a matrix as compared to an individual crosspoint relay with a cover sheet covering all of the crosspoints; and

FIG. 4 is a graphic representation of the pickup and dropout values of the crosspoint relays of a matrix relative to an individual crosspoint relay with a cover sheet covering a part of the crosspoint relays according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 there is shown a matrix with 8 times 8 bistable crosspoints arranged in rows and columns, with the crosspoints arranged in the center of the matrix being indicated by the reference numeral 1 while those arranged at the edges and the corners of the matrix being indicated by the reference numerals 2 and 3 respectively. Each of the crosspoints l, 2, 3 is associated with a permanent magnet and a coil. The permanent magnets of the crosspoints l, 2, 3 in the rows of the matrix are polarized in the same sense, and those in the columns are each polarized in the opposite sense. The axes of magnetization of the permanent magnets are in the same plane; the direction of magnetization is indicated in FIG. 1 by the arrows. Directly over the permanent magnets associated with the crosspoints 1, 2, 3 and in parallel with the plane in which the axes of magnetization of the permanent magnets are in, there is arranged a common cover sheet 4. This cover sheet 4 is so designed as to completely cover the permanent magnets associated with the crosspoints 1 arranged in the center of the matrix, and as to cover only half of the permacorners of the matrix are only partly covered, the magnetic shunt is reduced at these points. This compensates for the difference influence by the stray fields of the neighboring magnets. I

The mode of operation of the invention will be better understood by referring to the diagrams of FIGS. 2,3

and 4 showing the pickup and dropout values of the crosspoints of a matrix compared to a'single crosspoint outside the matrix. The respective pickup values are plotted on the X-axes of the diagrams while the respective dropout values are plotted on the Y-axes. No real values are shown on these plots, however, the pickup values increase in relation to the distance along the X- axis, and the dropout values increase in relation to distance along the Y-axis. As in FIG. 1, the crosspoints arranged in the center are also indicated in FIGS. 2 to 4 by the reference numeral 1 while those arranged at the edges and at the corners are indicated by the reference numerals 2 and 3 respectively. For the sake of compensation there is each time additionally shown the position of an individual crosspoint 5 not arranged in a matrix.

FIG. 2 shows the static values relating to a matrixwithout a cover sheet. The magnetic fields of the crosspoints 1 arranged inside (in the center of) the matrix additively combine with each other. This causes an increased magnetic flux through the open contacts. The pickup values of the crosspoints 1 decrease noticeably while the dropout values are shown to increase. The crosspoints 2, arranged along the edges of the matrix, show small variations of their values compared to those of an individual crosspoint 5. The values of the crosspoints 3 as arranged at the corner points of the matrix vary still less.

FIG. 3 shows the static values relating to a matrix in which all crosspoints are covered by a cover sheet. By this the values of all crosspoints 1, 2, 3 are caused to be displaced in such a way that the pickup values are increased while the dropout values decrease.

FIG. 4 shows the values relating to a matrix in which the cover sheet is cut away at the edges and corners as shown in FIG. 1. This further reduces the pickup values of the crosspoints 2 and 3 as arranged at the edges and corners, thus approaching the static-values of the crosspoints 1 arranged in the center of the matrix.

The variations in the pickup and dropout values of the individual crosspoints within a matrix which occur between the crosspoints near the center of the matrix, and those at the edges and corners of the matrix can therefore be eliminated by the use of a magnetic flux shunting cover. The larger fields causing lower pickup and higher dropout values at the center of the matrix due to the mutual combination of adjacent magnetic fields is thereby overcome by shunting the effects each 4. magnet would have on the adjacent crosspoint in the matrix. The shunting effect is only partial at the edges since the cover-sheet only covers half the crosspoint at the edges, and there is no shunting 0f the magnetic fields at the corners of the crosspoint matrix since the cover sheet does not cover any of thecrosspoints at the edges.

While we have described above the principles of our invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope.

of our invention as set forth in the objects thereof and in the accompanying claims.

What is claimed is:

1. In a crosspoint matrix of the type having a plurality of electromagnetic relays arranged in rows and columns, each relay including an electromagnetic coil and a permanent magnet, wherein the improvement comprises:

a cover sheet in magnetic proximity to said plurality of relays for selectively shunting the magnetic fields of the permanent magnets by partially covering some of the magnets and completely covering the rest of the magnets within said matrix thereby eliminating variations in magnetic forces upon the contacts within said relays.

2. A crosspoint matrix according to claim 1 wherein said cover sheet completely covers the permanent magnets near the center of said matrix and partially covers the permanent magnets at the edges of said matrix.

3. A crosspoint matrix according to claim 2 wherein said cover sheet is superimposed on said permanent magnets to cover half of each permanent magnet along the edges of said matrix and wherein the permanent magnets at the corners of said matrix are uncovered.

4. A crosspoint matrix of the type having a plurality of electromagnetic relays arranged in rows and columns, each relay containing an electromagnet and a permanent magnet, wherein the improvement comprises a common cover sheet placed on the permanent magnets parallel with the plane of the magnetization axes of said permanent magnets, said cover sheet entirely covering all the permanent magnets belonging to the interior rows and columns of said matrix, said cover sheet covering onehalf of each permanent magnet belonging to the outer rows and columns of said matrix, the permanent magnets at the corners of said matrix being uncovered, whereby the fields corresponding to said permanent magnets belonging to the interior rows and columns of said matrix are shunted to a greater extent than the fields of said permanent magnets belonging to the outer rows and columns of said matrix, and the fields of said permanent magnets belonging to the outer rows and columns of said matrix are shunted to a greater extent than the perm anent magnets corresponding to the corners of said matrix. 

1. In a crosspoint matrix of the type having a plurality of electromagnetic relays arranged in rows and columns, each relay including an electromagnetic coil and a permanent magnet, wherein the improvement comprises: a cover sheet in magnetic proximity to said plurality of relays for selectively shunting the magnetic fields of the permanent magnets by partially covering some of the magnets and completely covering the rest of the magnets within said matrix thereby eliminating variations in magnetic forces upon the contacts within said relays.
 2. A crosspoint matrix according to claim 1 wherein said cover sheet completely covers the permanent magnets near the center of said matrix and partially covers the permanent magnets at the edges of said matrix.
 3. A crosspoint matrix according to claim 2 wherein said cover sheet is superimposed on said permanent magnets to cover half of each permanent magnet along the edges of said matrix and wherein the permanent magnets at the corners of said matrix are uncovered.
 4. A crosspoint matrix of the type having a plurality of electromagnetic relays arranged in rows and columns, each relay containing an electromagnet and a permanent magnet, wherein the improvement comprises a common cover sheet placed on the permanent magnets parallel with the plane of the magnetization axes of said permanent magnets, said cover sheet entirely covering all the permanent magnets belonging to the interior rows and columns of said matrix, said cover sheet covering one-half of each permanent magnet belonging to the outer rows and columns of said matrix, the permanent magnets at the corners of said matrix being uncovered, whereby the fields corresponding to said permanent magnets belonging to the interior rows and columns of said matrix are shunted to a greater extent than the fields of said permanent magnets belonging to the outer rows and columns of said matrix, and the fields of said permanent magnets belonging to the outer rows and columns of said matrix are shunted to a greater extent than the permanent magnets corresponding to the corners of said matrix. 